I think Amtrak California trains technically can leave the state, but either CA would have to be really nice and fund it or Nevada would have to chip in. If a service were to start, it wouldn't use a dedicated Amtrak line, but the UP's existing ROW. I think it could use a small number of CA Bilevels that are freed up from the San Joaquin Ventures, or it would use Horizons. But no matter what cars it used, it will add another strain to an already very strained system, equipment wise. And I don't think there are any concrete plans and even if there were it would be many years before it took off, so this is all just fantasy. It would definitely not use superliners though, they are way too limited.